Generally, frame panels have been typically used as supports in a variety of products. For example, a seat back of a car is provided therein with a frame panel, thus being reinforced and supported by the frame panel. The frame panel used in the seat back of a passenger car must efficiently support the weight of a person sitting on the seat. Furthermore, a frame panel used in the seat back of a truck must have a high structural strength capable of efficiently supporting the weight of a person sitting on the seat and efficiently resisting impact which may be applied by the freight loaded in the truck. In the case of a rear seat back frame, panel installed in the rear end of the passenger compartment of a passenger car, the frame panel must meet the European requirements ECE 17.07, which were established to protect passengers from impact, which may be applied by freight loaded in the trunk of the car without being fastened or fixed, when a driver suddenly stops the car while driving the car.
Conventional seat back frame panels have been typically made of steel. However, steel complicates the process of producing the frame panels and increases the weight of the frame panels because it is heavy. Furthermore, the steel frame panel is thick to secure desired strength, thus increasing the weight of the frame panel. When the weight of the frame panel increases as described above, the frame panel is difficult to handle and increases the weight of a car body, thus reducing the mileage of the car. Therefore, it is necessary to configure the seat back frame panel such that the seat back frame panel is both light and intrinsically secures substantial strength.
Accordingly, in recent years, techniques of using reinforced plastic as the material of the seat back frame panels in place of the conventional steel have been proposed. For example, glass mat thermoplastics (GMT) or long fiber reinforced thermoplastics (LFT) have been proposed to replace the conventional steel as the material of the seat back frame panels. Furthermore, to increase the strength of the reinforced plastic frame panel and to prevent the plastic frame panel from undesired bending, a plurality of ribs is formed as a reinforcing pattern on the plastic frame panel (first conventional technique). The plastic frame panel according to the first conventional technique is shown in FIG. 1.
FIG. 1 is a plan view illustrating the seat back frame panel according to the first conventional technique. FIG. 1 illustrates the most typical seat back frame panel. As shown in FIG. 1, the conventional seat back frame panel is typically made of reinforced plastic through a pressing process and comprises a plate body 1 and a plurality of ribs 1a, which is formed as a reinforcing pattern on the surface of the plate body 1.
However, the reinforced plastic frame panel having the structure shown in FIG. 1 is problematic in that it must be produced through a complex process and cannot be made light. Furthermore, the reinforced plastic used as the material of the frame panel is very expensive, which increases the cost of the frame panels. For example, the GMT (glass mat thermoplastic) is problematic in that it requires a complex pressing process and is very difficult to recycle. Furthermore, the GMT is 4˜5 times as expensive as steel.
In an effort to overcome the problem of the first conventional technique, Korean Patent Laid-open Publication No. 10-2004-0030082 (International Laid-open Publication No. WO. 2003/016091) discloses a seat system having a reinforcing pattern comprising a hollow pattern and a groove pattern (second conventional technique). The seat system according to the second conventional technique is shown in FIGS. 2 and 3.
FIG. 2 is a perspective view illustrating the seat back frame panel according to the second conventional technique. FIG. 3 is a sectional view taken along the line I-I in FIG. 2.
As shown in FIGS. 1 and 2, to produce a seat back frame panel, a front plate 2 and a rear plate 3 are separately produced through forming and, thereafter, the front plate 2 and the rear plate 3 are integrated with each other at joins 4 using an adhesive, thus forming a panel body. Furthermore, a hollow pattern 5, a groove pattern 6 and a protruding pattern 7 are formed as a reinforcing pattern on the panel body, so that a desired seat back frame panel is produced. In the seat back frame panel, the hollow pattern 5 and the groove pattern 6 provide advantages in that, due to the patterns 5 and 6, the frame panel can efficiently absorb shocks, increase the structural strength, and realize lightness.
However, the second conventional technique disclosed in the cited document is problematic in that, because the front plate 2 and the rear plate 3 are separately produced through forming and, thereafter, the front and rear plates 2 and 3 are laminated with each other at the joins 4 using the adhesive to form the single panel body, the second conventional technique complicates the process of producing the seat back frame panels. Described in detail, the process of forming the front plate 2 and the rear plate 3, and the process of laminating the front and rear plates 2 and 3 with each other into a single panel body must be executed separately and independently, so that the process of producing the frame panel is complicated. Furthermore, when the front plate 2 and the rear plate 3 are laminated with each other into a single panel body at the joins 4, it is not easy to precisely arrange the plates 2 and 3 relative to each other, so that smooth or precise joins 4 are not provided. The above-mentioned problems experienced in the process of producing the frame panels increase the cost of the products. Particularly, because the frame panel disclosed in the cited document has the joins 4, the structural strength of the frame panel is reduced at the joins and, furthermore, the frame panel may break at the joins 4 when the frame panel is severely bent.